1. Field of the Invention
The present invention relates to an active matrix type liquid-crystal display (LCD) device which is driven by thin-film transistors (TFT's). More particularly, it relates to a TFT-LCD device of lower cost and higher performance.
2. Description of the Related Art
Demand has increased for active matrix type LCD devices of high cost performance and TFT drive mode. In order to comply with the demand, it is necessary to realize curtailment in the cost of a manufacturing process for the TFT-LCD device applying amorphous silicon (a-Si), that is, a reduction in the number of process steps, enhancement in the throughput of the manufacturing process and enhancement in the yield of the TFT-LCD device, and also to heighten the performance of the TFT-LCD device including capabilities for a large size, a high resolution and gray-scale representation. For such purposes, Japanese Patent Application Publication (KOKOKU) No. 26084/1992 has proposed an active matrix type display device comprising a plurality of column selection lines which are formed of a first conductor layer made of a transparent electrode film deposited on an insulating substrate, drain electrodes which are respectively integral with the corresponding column selection lines, display pixel electrodes which are arrayed at individual pixel positions, source electrodes which are respectively integral with the corresponding display pixel electrodes, a semiconductor layer which is formed on the insulating substrate so as to extend onto the drain and source electrodes, a plurality of row selection lines which are formed of a second conductor layer deposited on the semiconductor layer through a gate insulating layer, and gate electrodes which are respectively integral with the corresponding row selection lines, wherein the semiconductor layer and the gate insulating layer are patterned in the same shapes as those of the row selection lines and the gate electrodes integral therewith. With this structure, it is intended to simplify the manufacturing process and to enhance the reliability and yield of the TFT-LCD device owing to the prevention of the breaking of the electrode wiring lines.
The device structure based on the prior-art technique is very effective for simplifying the manufacturing process. It has been impossible, however, to say that contrivances for the higher performance, including the capabilities for the large size, high resolution and gray-scale representation, have proved satisfactory. Moreover, the curtailment in the cost has been difficult due to low yield.